Caution should be the byword when quoting the Koran

Tony Blair picked up the Koran again, we are told, as his in-flight reading on the way to Egypt on Thursday. He packs a copy of Islam's holy book, along with the Bible, into his suitcase for every trip. It is easy to see why.

The air is thick with quotations from the Koran. If you meet those who reject the words of the Prophet, quotes Osama bin Laden, it is your duty to strike at their necks. If you kill one innocent person, your sin will be as if you killed all humanity, moderate Muslims reply.

The Prime Minister is increasingly joining in the exchange. "To kill, as these terrorists did, is utterly foreign to all teachings of the Koran," Mr Blair told Al-Jazeera, the Middle East's best-watched television station, this week. "To justify it by saying such murder of the innocent is doing the will of God is to defame the good name of Islam."

It seems fortuitous that Mr Blair is the first British Prime Minister since Gladstone to have made a serious attempt to understand Islam. Many British Muslims appear impressed by his effort.

But there are dangers in his strategy. When he went on to tell the Al-Jazeera interviewer: "The version of Islam that the Taliban regime and Osama bin Laden support is a version of Islam a million miles away from the reality," the response was swift. "Isn't it the task of the Muslim world to see to that, not the Western Christian world?" his interlocutor said.

But there is a theological objection, of which most people in the West are unaware. Among Christians, disagreements over interpretation of the Bible are common: since the Protestant Reformation, Western culture has put less trust in the idea that interpretation can only be carried out by a single authoritative source.

But in Islam this breakdown has not occurred. There is a whole Islamic discipline called tafsir whose experts devote lifetimes of study to elucidation of individual verses of the Koran – particularly those that seem to contradict other verses.

For those who are not qualified scholars to fence with quotations from the Koran is, according to Hamza Yusuf, one of President George Bush's advisers on Islam, "like every American interpreting the constitution according to his whim and expecting it to be as valid as the opinion of a constitutional lawyer with years of training".

Over the centuries, tafsirscholars have divided the Koran's verses into categories – general and specific verses, universal and particular, ambiguous and clarifying. Systems have been set in place to make it clear that, in Mr Yusuf's words, "Islam is a holistic tradition in which no verse can be taken out of the context of the whole." Moreover, only those who have an ijaza, a licence, to show that they have an isnad, a documented, unbroken chain of authority that can be traced back to the Prophet, are considered under Islamic law to have the legitimacy to make such judgements.

The good news for Tony Blair is that Osama bin Laden has no such ijaza. But then neither does the British Prime Minister. Which is why, when it comes to the Holy Koran, caution should be the order of the day.